Cycle Backface culling didn't work
In Blender 2.79:
For your backface cull object, go to Object settings and at least disable shadow:

This material node setup is all you need for pure black:

Both shift-Z and F12 render work:

In Blender 2.80 (as of February 27, 2019):
Use the same material node setup as shown above for 2.79. Then go to Material tab and change Blend Mode to Alpha Clip (or something similar):

Cheers!